The disclosures herein relate generally to deep water pipeline construction and more particularly to an abandonment and recovery head apparatus for a pipeline.
When a pipeline must be abandoned from a pipelay vessel, an abandonment and recovery (A&R) head apparatus is welded to the end of the pipeline. A hook apparatus coupled to the vessel by a wire is connected to the A&R head apparatus, and the pipeline is lowered to the seabed by running wire off the vessel and down to the seabed until the A&R head apparatus is resting on the seabed.
The A&R head apparatus consists of an head welded to the end of the pipeline, with a lifting eye connected to the head. With the A&R head apparatus resting on the seabed, the lifting eye must be kept in a vertical position to enable detachment and reattachment of the hook apparatus to the lifting eye during abandonment and recovery of the pipeline. This is done by attaching a buoy to the lifting eye. A severe disadvantage of this lifting arrangement is that the buoy needed to keep the lifting eye vertical is long, heavy, and voluminous. The weight of the A&R head apparatus must be handled by the wire with hook apparatus. The length and the weight of the entire A&R head apparatus, hook apparatus, and wire are such that it is difficult and time consuming to line up the A&R head apparatus with the end of the pipeline and weld this connection to the pipeline when a pipe must be abandoned. The volume of the buoy is such that it is difficult and time consuming to pass the buoy by equipment on the vessel needed to lower or retrieve the pipeline.
Accordingly, it would be desirable to provide an abandonment and recovery head apparatus absent the disadvantages found in the prior methods discussed above.